FR: Specify FeaturesRouter per user

[dblythy]

I really like Parse Dashboard, and I'd really like to use it to share with my clients to allow them to manage their parse instances. However, there are a few changes I'd like to add:

Specify Features per user
I'd like to change which subsections are available depending on which user logs in. For example, some users I only want to be able to view /logs, whilst others the full dashboard.

Specify Collections and Columns in Data Browser
I only want certain users to be able to edit _User, whilst other admin users can only edit and view Photos. And certain other users I only want to be able to view certain columns of a class.

Let me know your thoughts!

[dblythy]

Also related to #1427